This invention relates to telephones in general and in particular to telephones having a receiver that is driven by either voice signals or ringing signals. More specifically, this invention relates to such a telephone having circuitry for attenuating the ringing signal when the telephone handset is displaced from a preselected position.
In recent years, we have witnessed the introduction of what is commonly referred to as the "cordless" telephone. These telephones are found in both the home and business. The cordless telephone is usually a two-piece apparatus; a base station and a cord-free, battery-powered handset that communicate with each other by transmitting and receiving signals through antennas. A typical cordless telephone uses the base station house wiring to radiate a low-frequency signal to the handset. Transmissions from the handset to the base are typically made at a much higher frequency. However, there are some cordless telephones which use the higher frequency for all transmissions. Furthermore, cordless telephones are generally of two types. In a first type, the handset has no keypad, and only the voice communications are radio linked between the base station and handset. In this first type of cordless telephone, the keypad is on the base station. The other type of cordless telephone has the keypad on the handset and all the normal functions of a telephone are linked to the base station.
In many cordless telephones the receiver doubles in its function and receives both transmitted voice signals and ringing signals. Thus, we not only hear the voice of the caller through the receiver, but it also replaces the conventional electromechanical bell as the ringing signal is now transmitted from the receiver. The receiver is basically an electromagnetic transducer which is capable of converting a varying electrical signal, i.e., voice signals or ringing signals, into variations in air pressure usable by the human ear.
A problem that frequently occurs as a result of the dual function of the receiver is referred to herein as "acoustical shock." On many cordless telephones a "talk" switch, which is found on the handset, must be operated in order to place the handset on-line making it ready for use. Acoustical shock occurs when the receiver is put to the users ear before operating the talk switch and upon a ringing signal being emitted from the receiver. Under these circumstances the user can be subjected to a sound that measures more than 100 decibels (dB).
This problem of acoustical shock can also occur in some one-piece telephone units which are picked up from their cradle, or from a surface without allowing their hookswitch to function.
It is the general objective of the present invention to provide a telephone which prevents the user from being subjected to acoustical shock as described above.
More specifically, it is the object of this invention to prevent the problem of acoustical shock by disposing between the telephone ringing circuitry and the receiver, a gravity switch in parallel connection with a resistive means. In combination, these elements reduce the sound level of the ringing signal upon the chance happening that the receiver is emitting a ringing signal when the receiver is placed near the user's ear.
Gravity or position-sensitive switches have been used in connection with telephones as shown in U.S. Pat. No. 379,074, "Electrical Contact Maker and Breaker," to C. Lambin; U.S. Pat. No. 2,140,655, "Radio Control Device," to C. J. Sloan; U.S. Pat. No. 3,365,554, "Prevention Of Dialing By A Telephone Switchhook," to A. M. Breyzinski; U.S. Pat. No. 3,683,103, "Headset With Circuit Control," to L. R. Kahn; and European Patent Application No. 0063672, "Telephone Music Device," to R. K. L. Tang, et al.